Display system with rapid color switching

ABSTRACT

An improved color display system employing a beam penetration type cathode-ray tube with rapid color switching. The screen electrode is separated from the accelerating electrodes without the use of an isolating mesh so that the voltage applied to the screen electrode is switched across only a relatively small capacitance. The invention may be used in conjunction with either magnetic or electrostatic deflection beam penetration cathode-ray tubes as well as either magnetic or electrostatic focus tubes. Such display systems may be used for radar type random access or scanned raster type displays.

SWITCHING lhiited States atent 119i [iii 3,840,773 Hart [45] Oct. 8,1974 [54] DISPLAY SYSTEM WITH RAPID COLOR 3,603,830 9/1971 Ganar@ et ai.313/92 PF [76] Inventor: Harold M. Hart, 5 Marvin Rd., lfggllldbisbasmnWellesley Mass 02181 Attorney, Agent, or Firm-Joseph D. Pannone; Milton[22] Filed: Dec. 29, 1972 D. Bartlett; David M. Warren [2l] Appl. No.:319,968 [57] ABSTRACT An improved color display system employing a beam[gi] JSCCII' 315/29 313/65 T 3%/1l.5259 penetration type cathode-raytube with rapid color [58] Flitid 28 J29 /17 switching. The screenelectrode is separated from the "134001 8g Si) 343 5 acceleratingelectrodes without the use of an isolating C/D mesh so that the voltageapplied to the screen electrode is switched across only a relativelysmall capaci- 56 R f Ct d tance. The invention may be used inconjunction with 1 e erences l e either magnetic or electrostaticdeflection beam pene- UNITED STATES PATENTS tration cathode-ray tubes aswell as either magnetic or 2,455,710 12/1948 Szegho 313/92 PFelectrostatic focus tubes. Such display systems may be 2.590.018 3/ 1952Koller etal. 3l3/92 PF used for radar type random access or scannedraster 3,114,907 12/1963 Lufiman e; a1 343/5 CD type displays. 3,270,2348/l966 Schaffernicht et al. 313/83 SP 3,428,858 2/1969 Giypiis 313/92 PF22 Claims, 4 Drawing Figures 9 x 56 g) sa ii/ y i@ 75 t 93 98 5/ 74 j i90 T i 37 56 y2 40 ss 141 Racen/ER WDEO l`l g 4/ AMP 92' /05 /03 /07 f372 ,Ye Y ;"M'Mw RAMP I xdlg GEN. 9%-- ad/ 99 'DDJ 6 977 vlii'AGE SUPPLYl /U --Y 42 2O 2/ L COLOR 43 VAFrliIIAGLE HMM CONTROL MME-4M' VOLTAGECIRCUIT SUPPLY /5 DISPLAY SYSTEM WITH RAPID COLOR SWITCHING BACKGROUNDOF THE INVNTION Numerous prior art attempts have been made to constructmultiple color cathode-ray tube systems in which the color is varied bychanging the screen anode voltage and hence the beam velocity and thepenetration depth of the electron beam into a multilayer phosphorscreen. The earliest of' these attempts included a cathode-ray tubewherein the screen electrode and conductive coating on the inside of thetube envelope formed a single electrode both connected to the same highvoltage source. These early attempts suffered from two major problems.First, the screen electrode and conductive coating connected togetherformed a large capacitance across which the high voltage had to beswitched each time the color was to be changed. This large capacitancecreated the need for a high powered amplifier which was capable ofswitching the voltage across such a capacitance in a relatively shortperiod of time, otherwise large delay times had to be tolerated if amore reasonably powered amplifier switch was used to the high voltage.Secondly, whenever the high voltage to the screen and conductive coatingwas switched, the deflection sensitivity of the tube also changed sincethe high voltage which was connected to these electrodes was the finalaccelerating voltage which is determinative of the deflectionsensitivity of the tube.

Later attempts divided the screen electrode from the conductive coatingon the inside of the tube envelope with a conductive wire mesh insertedbetween the two electrodes thus formed. Although the capacitance of thescreen electrode, with respect to the tube cathode and ground, wasreduced somewhat by the separation, the insertion of the mesh raised thecapacitance again to a higher capacitance since the mesh and screenelectrodes formed a parallel plate capacitor. Furthermore, such a meshcreated problems when the electron beam struck the wire of the mesh.

One attempt to circumvent the problem of having to switch a high voltageacross a large capacitance included a tube in which the screen electrodeand envelope coating electrode were connected together but two or moreseparate electron guns were used, one for each of the layers of phosphorin the screen. Each of these electron guns was connected to a differentvoltage so that the voltage between each gun and the screen wasdifferent. One problem with such multiple gun beam penetrationcathode-ray tubes was arcing between the guns as several kilovolts ofvoltage difference were typically required between the electron guns toachieve usable penetration depth differences. Furthermore, the potentialdifference between the electron guns created lensing effect in the gunregion which resulted in pattern distortion problems. Also, it wasnecessary to impress the video signals upon a relatively high voltagecompared with their normal voltage levels.

SUMMARY OF THE INVENTION The above stated as well as other objections ofthe prior art may be overcome by a multicolor cathode-ray tube havingmeans for providing an electron beam, tube envelope, and screen in whichis provided the combination of means for creating an electric field inthe region adjacent to the screen and means for applying a plurality ofvoltages to the electric field creating means. The electric fieldcreating means is located outside of the region traversed by the beam.The electric field creating means may be a plurality of electrodes or aspiral electrode located adjacent to the surface of the envelope of thecathode-ray tube.

Objections of the prior art may also be overcome by providing thecombination f means for focussing the beam of a cathode-ray tube, meansfor positioning the beam of the cathode-ray tube in proportion to one ormore independent signals and one or more electrodes for changing thecolor of the light emitted from the cathode-ray tube without affectingthe focus of the beam wherein the electrodes are located outside theregion traversed by the beam. The positioning means may comprise one ormore deflection amplifiers, each having at least one input and oneoutput, the inputs of which are coupled to the aforementioned inputsignals. These input signals may be generated from a computer such as acentral computer used in a radar display system where the radar data isfirst digitized for processing and then displayed at appropriate placesupon the screen of the display. The positioning means further mayinclude means for generating defiecting fields in response to theoutputs of the amplifiers. The deflecting field generating means maycomprise either deflection coils, such as a magnetic deflection yoke, orelectrostatic deflection plates located within the cathoderay tube. Theelectrodes mentioned above provide an electrostatic field such as anelectrostatic field produced by placing a screen electrode at onevoltage and one or more accelerating electrodes at other voltages. Sucha combination may be used in a display system, such as a radar displaysystem, which may be a random access display system or in a scannedraster television type display system.

Furthermore, the objections of the prior art may be overcome by thecombination of a beam penetration cathode-ray tube, one or moreelectrodes for changing the velocity of the beam of the tube located theregion traversed by the beam, means for focussing the beam whichoperates independently from and is not affected by the electrodes, andmeans for positioning the beam in proportion to one or more inputsignals. In this case, the focussing means may include means forproviding an electrostatic focussing lens, such as one normally used inan electron gun of a cathode-ray tube, and a magnetic focussing coil. i

Still further, the objections of the prior art may be overcome by thecombination of means for providing a focussed beam of electrons, aluminescent phosphor screen which, upon excitation, emits a plurality oflight colors, first and second voltage sources, a screen electrodeadjacent to the screen connected to the first voltage source, one ormore accelerating electrodes connected to the second voltage sourcelocated between the beam providing means and the screen electrode andoutside the path of the beam, means for varying the voltage of the firstvoltage source, and means for deflecting the beam to positions on thescreen determined by one or more input signals. In this case, the beamproviding means includes an electron gun. The phosphor screen comprisesa plurality of layers of phosphor particles. These plurality of layersmay be either a plurality of separated layers, each layer of which iscomposed of a single phosphor type or a layer of phosphor particles,

BRIEF DESCRIPTION OF THE DRAWINGS The aforementioned objects and otherfeatures of the invention are explained in the following descriptiontaken in connection with the accompanying drawings wherein:

FIG. 1 is a cross-sectional view of first type of cathode-ray tube usedin a radar data display system in accordance with the present invention;

FIG. 2 is a cross-sectional view of the screen of one type of acathode-ray tube;

FIG. 3 is a cross-sectional view of the screen of a second type ofcathode-ray tube; and

FIG. 4 is a cross-sectional view of an alternate type of cathode-raytube used in a scanned raster display system in accordance with thepresent invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT In FIG. 1 a cathode-ray tube,shown generally at 47, is used in a display system in accordance withthe present invention. In this tube 47, the electron gun 61 is astandard electron gun as is used in a monochrome cathode-ray tube. Theelectron gun 61 produces a single electron beam rather than a pluralityof electron beams as used in some multiple color cathode-ray tubes. Inthis electron gun, the cathode 33, heated by filament 64, emitselectrons which are focussed into a beam by focussing electrodes 36 andaccelerated towards the screen by the first accelerating electrode 35.The first accelerating electrode 35 is coupled to fixed high voltagesupply through conductive coating 38.` The magnetic deflection yoke 18deflects the beam to the desired position on the screen 62 as in mostcathode-ray tube systems. In the particular embodiment of the inventionshown in FIG. 1, the conductive coating 38 on the inside of the glasstube envelope 37 extends from the electron gun region towards the frontof the tube and completely covers the inside of the tube envelope 37 inthe region between the electron gun 61 and gap 46 thereby forming asecond accelerating electrode at the same voltage as the firstaccelerating electrode 35 as the two are electrically connected. Anonconductive gap 46, for example, lVz inches in width, separates theconductive coating 38 from a second region of conductive coating 39connected to the aluminization layer 40 forms the screen electrode. Thesecond conductive coating region 39 extends from the aluminization layer40 to one side of the gap 46, for example, 3.5 inches from the edge ofthe aluminization layer 40. The width of gap 46 is chosen along with thewidth of the second conductive coating 39 to have dimensions which willminimize the electrostatic field concentrations and hence lensingeffects within the region near the screen 4l of the tube as the propergap width of gap 46 will greatly reduce the strength of theelectrostatic lens formed by the voltage difference between the firstconductive coating 38 and second conductive coating 39. Furthermore,locating the gap at some distance from the screen tends to linearizenon-linear peripheral fringing effects that would be created if the gapwere located nearer the screen thereby reducing potential positionaldistortion near the edges of the screen 41.

In other embodiments of the invention there are a plurality of gaps suchas gap 46 to further reduce the strength of the electrostatic lenses andhence further reduce positional distortion caused by such electrostaticlenses. In some 0f these embodiments, with multiple gaps and hencemultiple accelerating electrodes, the electrodes may each be set at adifferent voltage. In still further embodiments of the presentinvention, the conductive coating on the inside of the tube envelope maybe fashioned in the form of a spiral or helix with the end nearest theelectron gun at one voltage and the end nearest the screen electrode ata second voltage. In such cases, the screen electrode may be connectedto one end of the helix or it may be connected to a separate highvoltage supply. Such a system will be discussed later in conjunctionwith FIG. 4.

In any of the embodiments of the present invention, there need be noconductive mesh between the screen electrode and the electrode orelectrodes formed on the inner surface of the tube envelope. Thus, onlya comparatively small capacitance need be switched, i.e., thecapacitance formed by the screen electrode 40 and the reference groundof the screen electrodes high voltage power supply which is mostcommonly the system ground. In most applications, this capacitance tendsto be minimal in that the screen must be exposed for viewing and henceis not usually near or parallel to any large metallic or conductivesurfaces with which relatively large capacitances may be formed. Incontrast, the capacitances formed from the electrodes on the conductivesurface of the tube envelope which, in many applications are eithersurrounded by a grounded metallic shield or are near a groundedconductive chassis or other such components within the console in whichit is customarily mounted, are much higher. Hence, if an attempt weremade to switch these electrodes, the capacitance across which the highvoltage must be switched is correspondingly higher. With the capacitancereduced across which the high voltage which must be switched in order tochange colors the switching time between colors is reduced making thecathode-ray tube useful in many applications in which it formerly couldnot be used because of the long switching times or high amplifier powerrequired.

Again referring to the embodiment shown in FIG. 1, a fixed high voltagesupply 20 is connected through a metallic connector 48 through the glasstube envelope 37 to the conductive coating 38. Similarly, a variablehigh voltage supply 21, used to change the potential of the electrode 40and hence the displayed color, is connected through metallic connector49 through the glass envelope 37 to the conductive coating 39. Theconductive coating 39 is connected to the aluminization layer 40 so thatthe aluminization layer 40 is at the same potential as the conductivecoating 39. A multilayer phosphor coating 41 is placed between thealuminization layer 40 and the front of the screen. The electron beam 46easily penetrates the thin aluminization layer 40 and strikes thephosphor layer 4l with a velocity determined by the voltage of variablehigh voltage supply 2l. Light, which is emitted from the phosphor layer41 when excited by the electron beam 56, is reflected from thealuminization layer 40 towards the front of the screen therebyincreasing the available light output of the tube.

Referring now to FIG. 2, there is shown a crosssectional view of thescreen 62 of the cathode-ray tube of F IG. 1. The phosphor layer 41consists of multilayered phosphor particles in which the differentlayers are each a different `type of phosphor. For example, the innerlayer 51 of one such particle is surrounded by an outer layer 50 ofanother type phosphor with an inert layer 51A separating the two. Theinert layer 51A absorbs electron energy without absorbing light therebyincreasing the voltage difference necessary to change colors. Improvedcolor resolution is thereby attained since the electron beam containstypically a range of electron velocity rather than a single velocity.The inner layer 51 may, for example, be a green light emitting phosphorwhile the outer layer 50 is a red light emitting phosphor. When theelectron beam 56 penetrates through the aluminization layer 40 andstrikes the phosphor layer 41 with a comparatively low velocity, thebeam will only penetrate the first layer 50 of the phosphor and will notreach the inner layer 51 as the energy of the electrons is substantiallycompletely absorbed in penetrating and exciting the first layer 50. Asthe electron beam velocity is increased and the electrons acquire highermomentum, the beam will penetrate deeper insider the phosphor particlesand eventually penetrate through inert layer 51A into the inner layer5I. If the inner phosphor layer 51 has a higher light emittingefficiency than the outer layer S0, the light emitted from the innerlayer 51 will be the predominant light output from the phosphor layer 4lat the comparatively higher beam velocities.

Referring now to FIG. 3, there is shown an alternative method ofconstructing a multiple layer beam penetration type screen. Here, thephosphor layer 41 contains phosphor particles, each with light emittinglayers 52 and 53, each of a different type of phosphor, separated byinert layer 53A. For example, the first layer 52 may be a phosphor whichemits predominantly red light while the layer 53 is composed of phosphorparticles 55 which emit predominantly green light. At comparatively lowbeam velocities, the beam will penetrate only into the first layer 52and not through the second layer 53. The layer 53, when its phosphorparticles are not excited, and inert layer 53A are relativelytransparent to the light emitted from the first layer 52. As the beamvelocity increases, electrons will penetrate through layer 52 and intothe layer 53. If the phosphor particles 55 of layer 53 are of-a higherefficiency phosphor than i the particles 54 of layer 52, the total lightemitted from the tube will be predominantly the color emitted from thesecond layer 53 at the higher electron beam velocity. Inert layer 53Aserves the same purpose as layer 51A in FIG. 2.

In either embodiment shown in FIG. 2 or FIG. 3 more than two layers ofphosphor may be used. For example, a third level of phosphor could beadded between layers 5l and 50 in FIG. 2 or a third layer of phosphorparticles inserted either between or on one side of phosphor layers 52and 53 in FIG. 3 along with appropriate inert layers. Furthermore, onelayer such as the layer 41 in FIG. 2 could be used in place of one ofthe layers 52 or 53 in FIG. 3 thereby `forming a three-color tube. Ifthe layer 41 in FIG. 2 were substituted for layer 53 in FIG. 3, at lowelectron beam velocity only the particles 54 in layer 52 would beexcited. As the beam velocity increased to intermediate values, theouter layer would be excited and at the higher electron beam velocitiesthe inner layer of phosphor 51 would finally be excited.

Referring again to FIG. 1, the cathode-ray tube 47 will be described inits use in a random access radar display system in accordance with thepresent invention. Radar target returns received by radar antenna andamplified and demodulated by radar transmitter/- receiver 81 areconverted to digital form by digitizer 82. The digitized radar signalsare coupled to central computer 83 where they are converted along withdata on lines 85 from peripheral units by pre-programmed instructions tothe proper format for visual presentation. The data on lines 85 mayinclude operator instructions such as desired radar range as well asancillary data such as weather maps or target identification symbols.The central computer 83 may be capable of supplying data to severaldisplay units 16 such as shown within the dotted lines of FIG. 1. Datais coupled from the central computer 83 to the display controller 10 ofthe display unit 16 on lines 57. The display controller includes arefresh memory for maintaining the visual presentation of data in aflicker-free condition. Use of a refresh memory within displaycontroller 10 frees the central computer 83 from having to perform therefresh function. The display controller 10 also provides data couplingand control signals to vector generator 11, character generator l2 andcolor control circuit I5. In order to cause the system to write aline,such as part of a weather map or radar target, the display controller l0on lines 58 sends to the vector generator ll the start and end pointcoordinates of the line which is to be written. The vector generator 11converts this beginning and end point information to time varying X andY position signals representing points on the line to be traced out.These position signals are connected out of the vector generator onlines 25 and 26 respectively. The output on line 27 includes informationas to when the cathode-ray tube beam 56 is to be blanked and unblankedand at what level of brightness the line is to be written.

The display controller 10 generates signals on lines 60 to the colorcontrol circuit 15 which determine which color should be used in writingthe displayed lines or characters. The color control circuit 15 on line43 signals the variable high voltage supply 21 indicating the propervoltage to apply to the screen electrode for the desired beampenetration and hence the proper color. Also, the color control circuit15 indicates the proper amplifier gain on line 42 for the X axisamplifier 17 and the Y axis amplifier 19 for the deflection sensitivitydetermined by the high voltage settings. It should be noted, however,that the deflection sensitivity changes with a tube such as illustratedin FIG. l is significantly less than the deflection sensitivity changesif the screen electrode and conductive coating were at the same voltageand were changed at the same time to change the color. The color controlcircuit 15 indicates the selected color on line 63 to video amplifier 14for brightness adjustments among the various colors.

Similarly, on lines 59 the display controller 10 transfers data to thecharacter generator 12 concerning the characters to be written. Theposition on the face of the cathode-ray tube may either be set throughthe character generator 12 or through the vector generator 11. Thecharacter generator 12 receives character code inputs on lines 59 fromcomputer controller 10 and l2 converts the codes to time varying X and Ydeflection signals on lines 28 and 29 respectively, thereby causing thebeam to trace out the desired character pattern. The character generatoralso produces a video signal on line 30 which causes the video amplifier14 to blank and unblank the beam 56 and to select the appropriatebrightness by varying the applied voltage on line 34 and hence the beamcurrent flowing from the cathode 33 of the electron gun 61.

Switches 22, 23 and 24 select either the vector generator 11 orcharacter generator 12 as inputs to the X and Y axis amplifiers on lines65 and 66 through pattern correction circuit 13 and on line 67 to videoamplifier 14. The switch position is chosen through the computercontroller through lines not shown in the drawing. Switches 22, 23, and24 are preferably high speed electronic switches.

The pattern correction circuit 13 receives X and Y inputs on lines 65and 66 respectively and applies a correction factor to these signalsprior to final amplification to correct for the fact that the surface ofthe screen of the cathode-ray tube 47 is more nearly flat thanspherical. If this correction were not made, the pattern on the face ofthe cathode-ray tube would be severely distorted. For example, if asquare box were to be drawn, the sides of -the box would appear curvedinwards.

The electron beam 56 is focussed by the voltage applied to focussingelectrodes 36 by focus control 44 on line 45. Since the electrostaticlens formed between conductive coatings 38 and 39 is extremely weak inthe area near the electron gun 61, the beam focus is unaffected bychanges in color. Hence, the focus control'44 need not be coupled tocolor control circuit 15.

The X axis amplifier 17 and Y axis amplifier 19 receive their correctedinputs on lines 31 and 32 respectively. These amplifiers provide thecorrect signal levels for beam deflection to the deflection yoke 18which contains both X and Y deflection coils. As mentioned previously,the gain of the X axis amplifier 17 and Y axis amplifier I9 are properlyset for the chosen color by the color control circuit on line 42.

FIG. 4 shows an alternative method of constructing a display system inaccordance with the present invention. In the system of FIG. 4, thecathode-ray tube shown generally at 105 has two main areas of differencefrom the cathode-ray tube in FIG. l. First, the two regions ofconductive coating 38 and 39 in FIG. 1 are here replaced by a frontsection of conductive coating 75 connected to a helical strip ofconductive coating 74 on the inside of the tube envelope 109. A variablehigh voltage power supply 21, as in FIG. 1, is connected to the frontsection of conductive coating 75 and the fixed high voltage power supply20 is connected to the end of the helical strip of conductive coating 74nearest the electron gun shown generally at 61. The second maindifference with the cathode-ray tube 105 is that deflection of theelectron beam 56 is accomplished by elec trostatic deflection plates 72and 73 rather than with a magnetic deflection yoke as used in the systemof FIG. l. The electron gun 61 and the screen 62 are the same as shownin FIG. 1. It is to be understood, of course, that the helical strip maybe used with magnetic deflection as can the two separate regions ofconductive coating be used with electrostatic deflection.

The cathode-ray tube 105 is shown used in a swept raster display system.Remotely transmitted signals are intercepted by antenna 93 and coupledto receiver 92.

In some embodiments, signals may be coupled from a radar receiver andprocessor or other signal source through a cable thus eliminating theneed for a receiver. The receiver 92 generates combined X and Y axissync signals on line 102, demodulated video information on line 106, andcolor information on line 108. The video amplifier 89 amplifies thevideo signal to the proper voltage level and couples it to the cathodeof the cathode-ray tube 105 on line 107. The sync circuit 91 separatesthe combined sync signal on line 102 and generates separate X and Y axissync signals on lines 101 and 100 respectively.

When the raster is being generated in the usual fashion with the scannedlines parallel to the X axis, there is one sync pulse for the Y axis fora number of sync pulses for the X axis equal in number to the number ofscanned lines in the presentation. The Y sync pulse starts thegeneration of the Y axis ramp in Y ramp generator 88 on line 99 whilethe X sync pulse starts the generation of the X axis ramp in X rampgenerator on line 98. Lines 103 and 104 coupling the output ramp signalsbetween the two ramp generators are necessary for corrections to theramp waveforms dictated by the fact mentioned previously that in thepreferred embodiment the face of the cathode-ray tube is more nearlyflat than round. The outputs of the X axis amplifier 87 on lines 94 and95, which are preferably equal in magnitude but opposite in polarity,are coupled to the X deflection plates 73 while the outputs of the Yaxis amplifier 86, similarly equal in magnitude but opposite inpolarity, are coupled to the Y deflection plates 72.

The color control circuit l5 receives information pertaining to thecolor to be displayed on line 108 from receiver 92. Its operation is thesame as that for the color control circuit of FIG. 1.

Although a preferred embodiment of the invention has been described,numerous modifications and alterations would be apparent to one skilledin the art without departing from the spirit and scope of the presentinvention. For example, the circuit of FIG. 4 may be used with thecathode-ray tube Aof FIG. 1 and vice versa. Numerous arrangements oflayered phosphors may also be used. A radial scanning mode as used in aplan position indicator color display presentation is also well withinthe scope ofthe invention. Furthermore, many different arrangements maybe used for the electrodes formed from the conductive coating on theinside of the tube envelope. Materials other than glass may be used forthis envelope. Although electrostatic focussing means has been describedin conjunction with the preferred embodiments, magnetic focussingemploying a standard focussing coil may be used as well.

What is claimed is:

1. In combination:

means for providing a beam of electrons;

a beam penetration luminescent phosphor screen, the color of lightemitted from said screen being dependent upon the velocity of theelectrons in said beam;

means for providing first and second voltage sources;

a screen electrode adjacent to said screen, said screen electrode beingconnected to said first voltage source and said screen electrodeaccelerating `said beam of electrons to a final impingement velocity;

an accelerating electrode, said accelerating electrode 'being locatedbetween said beam providing means and'said screen electrode and outsidethe path of said electron beam, and said accelerating electrode beingconnected to said second voltage source;

means for varying the voltage of said first voltage source, the voltageof said second voltage source being fixed at a predetermined value; and

means for deflecting said beam to positions on said screen determined byone or more input signals, said deflecting means being disposed betweensaid beam providing means and said accelerating electrodes.

2. The combination according to claim l wherein said beam providingmeans comprises an electron gun.

3. The combination according to claim l wherein said phosphor screencomprises a plurality of layers of phosphor particles.

4. The combination according to claim 1 wherein said phosphor screencomprises a layer of phosphor particles, each of said particlescomprising a plurality of concentric layers of phosphors each of saidlayers emitting a different color light upon excitation.

5. The combination according to claim 3 wherein said screen electrodefurther comprises a layer of` metal. y

6. The combination according to claim 5 wherein said metal is aluminum.

7. The combination according to claim l wherein said deflecting meanscomprises means for generating deflecting fields in response to theoutputs of deflection amplifiers.

8. The combination according to claim 7 wherein said deflecting fieldgenerating means comprises deflection coils.

9. The combination according to claim 7 wherein said deflecting fieldgenerating means comprises electrostatic deflection plates.

10. The combination according to claim 1 further comprising utilizationmeans in a display system.

l1.. The combination according to claim 10 wherein said display systemcomprises a randomaccess display system.

l2. The combination according to claim 10 wherein said display systemcomprises a scanned raster display system.

13. The combination according to claim 7 further comprising deflectionamplifier means coupled to said means for generating deflecting fields.

14. A display system comprising in combination:

means for providing a beam of electrons;

a beam penetration luminescent phosphor screen,

the color of light emitted from said screen being dependent upon thevelocity of the electrons in` said beam; means for providing first andsecond voltage sources;

a screen electrode adjacent to said screen, said screen electrode beingconnected to said first voltage source and said screen electrodeaccelerating said beam of electrons to a final impingement velocity;

an accelerating electrode, said accelerating electrode being locatedbetween said beam providing means and said screen electrode and outsidethe path of said electron beam, and said accelerating electrode beingconnected to said second voltage source;

means for varying the voltage of said first voltage source;

means for deflecting said beam to positions on said screen determined byone or more input signals, said deflecting means being disposed betweensaid beam providing means and said accelerating electrodes; and

signal receiving means, the voltage of said first voltage source varyingin response to signals received by receiving means.

15. The combination of claim 14 wherein said signal receiving meanscomprises radar signal receiving means.

16. The combination of claim 15 further comprising computer meanscoupled to one or more outputs of said radar signal receiving means.

17. The combination of claim 16 further comprising means for producingsignals corresponding to target positions on said screen in response tooutputs from said computer means.

18. The combination of claim 17 wherein said means for varying thevoltage of said first voltage source operates in response to outputsfrom said computer means, the color of data being displayed being variedin response to said outputs.

19. A random access display system comprising in combination:

means for providing a beam of electrons;

a beam penetration luminescent phosphor screen, the color of lightemitted from said screen being dependent upon the velocity of theelectrons in said beam;

means for providing first and second voltage sources;

an accelerating electrode, said accelerating electrode being locatedbetween said' beam providing means and said screen electrode and outsidethe path of said electron beam, and said accelerating electrode beingconnected to said second voltage source;

' a screen electrode adjacent to said screen, said screen electrodebeing connected to said first voltage source and said screen electrodeaccelerating said beam of` electrons to a final impingement velocity;

means for varying the voltage of said first voltage source;

means for deflecting said beam to positions on said screen determined byone or more input signals, said deflecting means being disposed betweensaid beam providing means and said accelerating electrodes;

deflection amplifier means coupled to each of said deflecting means;

vector generator means coupled to said deflection amplifier means; and

character generator means coupled to said deflection generator means.

20. The combination of claim 19 further comprising computer meanscoupled to said vector generator means, said character generator means,and said means for varying the voltage of said first voltage source, atleast some vectors and at least some characters being displayed on saidscreen being displayed in different colors.

21. A raster scanned display system comprising in combination:

means for providing a beam of electrons;

a beam penetration luminescent phosphor screen, the color of lightemitted from said screen being dependent upon the velocity of theelectrons in said beam;

means for providing first and second voltage sources;

a screen electrode adjacent to said screen, said screen electrode beingconnected to said first voltage source and said screen electrodeaccelerating said beam of electrons to a final impingement velocity;

an accelerating electrode, said accelerating electrode being locatedbetween said beam providing means and said screen electrode and outsidethe path of said electron beam, and said accelerating electrode beingconnected to said second voltage source;

means for varying the voltage of said first voltage source;

means for deflecting said beam to positions on said screen determined byone or more input signals, said deflecting means being disposed betweensaid beam providing means and said accelerating electrodes;

deflection amplifier means coupled to each of said deflecting means; and

means for producing signals for generating a raster scan pattern on saidscreen, said signal producing means being coupled to said deflectionamplifier means.

22. The combination of claim 2l wherein at least some lines of saidraster scan pattern are displayed in different colors.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTIUN Patent NO- 3,840,773 Dated OCT.. 8, 1974 Invented@ Harold M. Hart It is certified thaterror appears in the above-identified patent and that said LettersPatent are hereby corrected as shown below:

Title page, the name of the Assignee, Raytheon Company, is not shown.

In the Claims Claim 19, column 10, lines 38-42, should follow lines43-47 (Paragraphs are reversed) gned and Sealed this twenty-frst D ay OfOctober 1975 [SEAL] A ttes t:

RUTH C. MASON C. MARSHALL DANN Attesting Officer C ommissimzer ofPatents and Trademarks UNITED STATES PATENT OFFICE CERTIFICATE OFCORRECTION Patent No. 3,840,773 Dated Oct. 8, 1974 Inventor(s) Harold M.Hart It is certified that error appears in the above-identified patentand that said Letters Patent are hereby corrected as shown below:

Title page, the name of the Assignee, Raytheon Company, is not shown.

In the Claims Claim 19, column l0, lines 38-42, should follow lines43-47 (Paragraphs are reversed) Signed and Sealed this twenty-frst D ayOf October 19 75 [SEAL] AES.'

RUTH C. MASON C. MARSHALL DANN Attesing Offcer Commissioner of Patentsand Trademarks

1. In combination: means for providing a beam of electrons; a beampenetration luminescent phosphor screen, the color of light emitted fromsaid screen being dependent upon the velocity of the electrons in saidbeam; means for providing first and second voltage sources; a screenelectrode adjacent to said screen, said screen electrode being connectedto said first voltage source and said screen electrode accelerating saidbeam of electrons to a final impingement velocity; an acceleratingelectrode, said accelerating electrode being located between said beamproviding means and said screen electrode and outside the path of saidelectron beam, and said accelerating electrode being connected to saidsecond voltage source; means for varying the voltage of said firstvoltage source, the voltage of said second voltage source being fixed ata predetermined value; and means for deflecting said beam to positionson said screen determined by one or more input signals, said deflectingmeans being disposed between said beam providing means and saidaccelerating electrodes.
 2. The combination according to claim 1 whereinsaid beam providing means comprises an electron gun.
 3. The combinationaccording to claim 1 wherein said phosphor screen comprises a pluralityof layers of phosphor particles.
 4. The combination according to claim 1wherein said phosphor screen comprises a layer of phosphor particles,each of said particles comprising a plurality of concentric layers ofphosphors each of said layers emitting a different color light uponexcitation.
 5. The combination according to claim 3 wherein said screenelectrode further comprises a layer of metal.
 6. The combinationaccording to claim 5 wherein said metal is aluminum.
 7. The combinationaccording to claim 1 wherein said deflecting means comprises means forgenerating deflecting fields in response to the outputs of deflectionamplifiers.
 8. The combination according to claim 7 wherein saiddeflecting field generating means comprises deflection coils.
 9. Thecombination according to claim 7 wherein said deflecting fieldgenerating means comprises electrostatic deflection plates.
 10. Thecombination according to claim 1 further comprising utilization means ina display system.
 11. The combination according to claim 10 wherein saiddisplay system comprises a random access display system.
 12. Thecombination according to claim 10 wherein said display system comprisesa scanned raster display system.
 13. The combination according to claim7 further comprising deflection amplifier means coupled to said meansfor generating deflecting fields.
 14. A display system comprising incombination: means for providing a beam of electrons; a beam penetrationluminescent phosphor screen, the color of light emitted from said screenbeing dependent upon the velocity of the electrons in said beam; meansfor providing first and second voltage sources; a screen electrodeadjacent to said screen, said screen electrode being connected to saidfirst voltage source and said screen electrode accelerating said beam ofelectrons to a final impingement velocity; an accelerating electrode,said accelerating electrode being located between said beam providingmeans and said screen electrode and outside the path of said electronbeam, and said accelerating electrode being connected to said secondvoltage source; means for varying the voltage of said first voltagesource; means for deflecting said beam to positions on said screendetermined by one or more input signals, said deflecting means beingdisposed between said beam providing means and said acceleratingelectrodes; and signal receiving means, the voltage of said firstvoltage source varying in response to signals received by receivingmeans.
 15. The combination of claim 14 wherein said signal receivingmeans comprises radar signal receiving means.
 16. The combination ofclaim 15 further comprising computer means coupled to one or moreoutputs of said radar signal receiving means.
 17. The combination ofclaim 16 further comprising means for producing signals corresponding totarget positions on said screen in response to outputs from saidcomputer means.
 18. The combination of claim 17 wherein said means forvarying the voltage of said first voltage source operates in response tooutputs from said computer means, the color of data being displayedbeing varied in response to said outputs.
 19. A random access displaysystem comprising in combination: means for providing a beam ofelectrons; a beam penetration luminescent phosphor screen, the color oflight emitted from said screen being dependent upon the velocity of theelectrons in said beam; means for providing first and second voltagesources; an accelerating electrode, said accelerating electrode beinglocated between said beam providing means and said screen electrode andoutside the path of said electron beam, and said accelerating electrodebeing connected to said second voltage source; a screen electrodeadjacent to said screen, said screen electrode being connected to saidfirst voltage source and said screen electrode accelerating said beam ofelectrons to a final impingement velocity; means for varying the voltageof said first voltage source; means for deflecting said beam topositions on said screen determined by one or more input signals, saiddeflecting means being disposed between said beam providing means andsaid accelerating electrodes; deflection amplifier means coupled to eachof said deflecting means; vector generator means coupled to saiddeflection amplifier means; and character generator means coupled tosaid deflection generator means.
 20. The combination of claim 19 furthercomprising computer means coupled to said vector generator means, saidcharacter generator means, and said means for varying the voltage ofsaid first voltage source, at least some vectors and at least somecharacters being displayed on said screen being displayed in differentcolors.
 21. A raster scanned display system comprising in combination:means for providing a beam of electrons; a beam penetration luminescentphosphor screen, the color of light emitted from said screen beingdependent upon the velocity of the electrons in said beam; means forproviding first and second voltage sources; a screen electrode adjacentto said screen, said screen electrode being connected to said firstvoltage source and said screen electrode accelerating said beam ofelectrons to a final impingement velocity; an accelerating electrode,said accelerating electrode being located between said beam providingmeans and said screen electrode and outside the path of said electronbeam, and said accelerating electrode being connected to said secondvoltage source; means for varying the voltage of said first voltagesource; means for deflecting said beam to positions on said screendetermined by one or more input signals, said deflecting means beingdisposed between said beam providing means and said acceleratingelectrodes; deflection amplifier means coupled to each of saiddeflecting means; and means for producing signals for generating araster scan pattern on said screen, said signal producing means beingcoupled to said deflection amplifier means.
 22. The combination of claim21 wherein at least some lines of said raster scan pattern are displayedin different colors.